DESCRIPTION: (Adapted from Applicant,s Abstract) This proposal seeks to identify new genes which are essential for pathogenesis and could be used as targets for antifungal therapies in the opportunistic fungal pathogen, Cryptococcus neoformans. To identify fungal genes that are essential for pathogenesis. "signature-taged" mutagenesis, a novel screen which has been highly successful in Salmonella, will be adapted for use in C. neoformans. Mutant strains of C. neoformans will be generated by insertion of a unique "signature- tag" randomly throughout the genome. The mutant strains will be pooled and injected into a mouse. A strain that fails to proliferate in the animal host will be identified by the absence of its "signature-tag" in the genomic DNA of the recovered pooled organisms. Strains which are confirmed to be less virulent, will be analyzed throughly and the genes which have been disrupted by the signature tag will be cloned and characterized. Genes that are promising new leads for antifungal targets will be chosen for future characterization.